|现在||do||doing||has/have done||has/have been doing|
|过去||did||was/were doing||had done||had been doing|
|将来||will do / be going to do||will be doing||will have done||will have been doing|
|过去将来||should/would do||should/would be doing||should/would have done||should/would have been doing|
be about + 不定式
- The team is about to play an important match.
- We are about to leave,so there is no time to drop in on her now.
be + doing(仅位移动词)
- I'm going to John's house next Sunday.
- He is leaving school in three months.